Stablecoin Types Explained: Fiat-Backed, Algorithmic, and Over-Collateralized

A stablecoin is a cryptocurrency whose value is pegged to a fiat currency or other asset. Its purpose is to eliminate the extreme price volatility of crypto assets and provide a stable unit of account and settlement for on-chain transactions and DeFi. Stablecoins are one of the most important pieces of infrastructure in the crypto ecosystem; their combined market cap has surpassed the hundreds of billions of dollars.

1. Why Stablecoins Are Needed

1.1 The Volatility Problem in Crypto Markets

The prices of crypto assets like Bitcoin and Ethereum are highly volatile — intraday swings exceeding 5% are routine. This volatility makes crypto assets unsuitable as a stable medium for everyday payments and financial activities.

1.2 The Core Functions of Stablecoins

Function	Description
Medium of exchange	The pricing and settlement tool in crypto trading (e.g., the BTC/USDT trading pair)
Store of value	A "safe haven" during market turbulence
DeFi infrastructure	The core asset in DeFi applications such as lending, liquidity pools, and payments
Cross-border payments	Low-cost, fast global value transfer
Fiat on-ramp	A bridge connecting traditional finance and the crypto market

1.3 Overview of the Stablecoin Market

The stablecoin market is dominated by a handful of leading projects:

• USDT (Tether) holds the largest market share
• USDC (Circle) is the most regulated and compliant stablecoin
• DAI is the largest decentralized stablecoin
• New stablecoins continue to emerge, and the competitive landscape keeps evolving

2. Fiat-Reserve Stablecoins

2.1 Basic Mechanism

Fiat-reserve stablecoins are issued by an issuing institution that holds fiat currency (or equivalent assets) as reserves, issuing tokens on a 1:1 basis. Users can redeem tokens for the equivalent fiat currency at any time.

Peg mechanism:

• Issuance: A user deposits $1 with the issuer and receives 1 stablecoin
• Redemption: A user burns 1 stablecoin and receives $1
• Arbitrage: If the market price deviates from $1, arbitrageurs mint or redeem to profit from the difference, pulling the price back to the peg

2.2 Major Projects

USDT (Tether)

• Issuer: Tether Limited
• Market cap: The largest among stablecoins; has held the top position for years
• Deployed chains: Ethereum, Tron, Solana, Avalanche, and many others
• Reserve composition: US Treasuries, commercial paper, cash and cash equivalents, etc.
• Controversy: Reserve transparency has long been questioned; while Tether publishes periodic attestation reports, it has not undergone a full financial audit

USDC (USD Coin)

• Issuer: Circle (co-founded with Coinbase through the Centre consortium)
• Deployed chains: Ethereum, Solana, Avalanche, Arbitrum, and others
• Reserve composition: Cash and short-term US Treasuries
• Key feature: The most compliant stablecoin; periodic attestation reports are issued by accounting firms
• Risk event: Briefly depegged in March 2023 due to the Silicon Valley Bank collapse (approximately $3.3 billion in reserves were held at SVB)

FDUSD (First Digital USD)

• Issuer: First Digital Labs
• Key feature: A stablecoin that has grown rapidly on exchanges like Binance
• Reserves: Cash and US Treasuries held by an independent custodian

2.3 Pros and Cons

Pros	Cons
Stable peg, strong market confidence	Relies on a centralized issuer; counterparty risk
Good liquidity, widely accepted	Reserve transparency depends on issuer self-discipline
Simple and easy to understand mechanism	Can be frozen or blacklisted (for compliance reasons)
Higher regulatory acceptance	Reserve asset safety is affected by the banking system

3. Over-Collateralized Stablecoins

3.1 Basic Mechanism

Over-collateralized stablecoins are minted by locking crypto assets worth more than the stablecoin's face value in a smart contract as collateral. Since the collateral itself fluctuates in price, over-collateralization provides a safety buffer.

3.2 Major Projects

DAI (MakerDAO)

DAI is the most successful decentralized stablecoin, issued by the MakerDAO protocol.

Minting process:

1. A user creates a Vault in MakerDAO
2. Deposits collateral (ETH, WBTC, RWA, etc.)
3. Mints DAI based on the collateral ratio (e.g., ETH's minimum collateral ratio is 150%; depositing $150 worth of ETH allows minting up to $100 in DAI)
4. The user pays a stability fee (annualized interest rate)
5. Upon repaying DAI plus the stability fee, the collateral can be withdrawn

Liquidation mechanism: When the collateral ratio falls below a threshold, the smart contract automatically liquidates the Vault, selling the collateral to repay the DAI debt.

DSR (DAI Savings Rate): MakerDAO governance can set a deposit rate (DSR) for DAI; users holding DAI can deposit it into the DSR contract to earn interest.

LUSD (Liquity)

• Mechanism: Accepts only ETH as collateral; minimum collateral ratio of 110%
• Key feature: One-time minting fee, no ongoing interest; fully decentralized with no governance token intervention
• Stability mechanism: Redemption mechanism (anyone can redeem 1 LUSD for $1 worth of ETH collateral)

crvUSD (Curve)

• Issuer: Curve Finance
• Key feature: Uses the innovative LLAMMA algorithm (Lending-Liquidating AMM Algorithm), which gradually converts collateral into stablecoins as prices fall, achieving "soft liquidation"

3.3 Pros and Cons

Pros	Cons
Decentralized, censorship-resistant	Low capital efficiency (requires over-collateralization)
Transparent and auditable; all data is on-chain	Cascading liquidations possible in extreme market conditions
No need to trust a centralized institution	Limited range of accepted collateral types
Deep integration possible with DeFi	More complex for users to operate

4. Algorithmic Stablecoins

4.1 Basic Mechanism

Algorithmic stablecoins attempt to maintain their price peg entirely through algorithms and smart contracts that regulate token supply and demand, without relying on fiat reserves or over-collateralized crypto assets.

4.2 Main Mechanism Types

Elastic Supply (Rebase)

Automatically adjusts each holder's token balance based on price deviation. Supply increases when the price is above $1, and decreases when below $1. Representative: Ampleforth (AMPL).

Seigniorage Model

Uses a dual-token system: one stablecoin and one governance/equity token. When the stablecoin's price deviates from its peg, supply is adjusted through minting or burning.

The Terra/LUNA Model (Collapsed)

UST (TerraUSD) was once the largest algorithmic stablecoin, maintaining its peg through a two-way minting/burning mechanism with LUNA. In May 2022, UST experienced a death-spiral depeg:

1. Large amounts of UST were sold off, pushing the price below $1
2. The arbitrage mechanism required minting massive amounts of LUNA to absorb the UST
3. The explosive increase in LUNA supply caused its price to crash
4. The LUNA crash further undermined market confidence in UST
5. UST ultimately fell to near zero, and LUNA's market cap was wiped out

This event caused approximately $40 billion in losses and is the largest algorithmic stablecoin failure in crypto history.

4.3 Fractional Algorithmic Stablecoins

Given the high risks of pure algorithmic stablecoins, some projects use hybrid mechanisms:

FRAX: Initially a fractional algorithmic stablecoin (partial reserves + partial algorithm), it has since gradually transitioned to a fully-reserve-backed model (FRAX v3), incorporating real-world assets like US Treasuries as reserves.

4.4 Challenges for Algorithmic Stablecoins

Challenge	Description
Death spiral	Loss of confidence triggers a vicious cycle of selling and minting
Cold start problem	Insufficient market depth and confidence during the early stage
Reflexivity risk	The algorithmic mechanism can accelerate collapse in extreme conditions
Historical track record	Failed cases of UST and other algorithmic stablecoins

5. Stablecoin Comparison Overview

Type	Examples	Peg Mechanism	Decentralization	Capital Efficiency	Risk Level
Fiat-reserve	USDT, USDC	Fiat/Treasury reserves	Low	High	Low-Medium
Over-collateralized	DAI, LUSD	Crypto over-collateralization	High	Low	Medium
Algorithmic	FRAX	Algorithm + partial reserves	Medium-High	High	Medium-High

6. Regulatory Developments

6.1 Global Regulatory Framework

Stablecoins, due to their direct link to fiat currency, have attracted intense scrutiny from regulators worldwide:

• United States: Pursuing stablecoin legislation that may require issuers to obtain a banking license or special permit.
• European Union: The MiCA (Markets in Crypto-Assets) regulation has established clear reserve and disclosure requirements for stablecoins.
• Singapore: The MAS has published a stablecoin regulatory framework with reserve requirements for single-currency-pegged stablecoins.
• Hong Kong: The HKMA is developing a licensing regime for stablecoin issuers.

6.2 Key Regulatory Concerns

• Adequacy and transparency of reserve assets
• Consumer protection and redemption guarantees
• Anti-money laundering and counter-terrorism financing compliance
• Systemic financial risk (potential impact of large stablecoins)

6.3 Impact on the Industry

Clearer regulatory frameworks will:

• Increase user confidence in stablecoins
• Phase out non-compliant issuers
• Potentially constrain the growth of decentralized stablecoins
• Pave the way for large-scale institutional adoption

7. Trends in Stablecoin Development

7.1 Yield-Bearing Stablecoins

Stablecoins that automatically generate yield (such as US Treasury returns) simply by holding them, upgrading stablecoins from a pure store of value to interest-bearing assets. Representative projects: sDAI (MakerDAO's DSR receipt) and Ethena's USDe.

7.2 RWA-Backed Reserves

An increasing number of stablecoins are incorporating low-risk real-world assets (RWAs) like US Treasuries into their reserves, generating yield while maintaining stability.

7.3 Expansion into Payment Use Cases

Stablecoins are expanding from a pricing tool for crypto trading into real-world payment scenarios. Traditional payment giants like Visa and PayPal have begun integrating stablecoin payments.

7.4 Multi-Chain Deployment

Native cross-chain stablecoin designs allow the same stablecoin to circulate seamlessly across multiple chains, reducing bridging risk.

Summary

Stablecoins are a critical bridge connecting traditional finance and the crypto world. From fiat-reserve USDT/USDC to decentralized DAI, and through the exploration and hard lessons of algorithmic stablecoins, stablecoin design continues to seek balance among security, decentralization, and capital efficiency. As regulatory frameworks mature and technology advances, stablecoins have the potential to become a core component of global digital payments and financial infrastructure.

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